Action Points

Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Although mothers have been identified as the source of the Streptococcus mutans bacteria that can cause tooth decay in their children, a genetic analysis of S. mutans strains suggested that there are many other sources.

Note that about half of the S. mutans strains found in the children over 8 years of follow-up were not shared by their mothers, or by other members of the household.

BOSTON -- Mom is off the hook -- at least partly when it comes to decay in their children's teeth.

Mothers have long been identified as the source of the Streptococcus mutans bacteria that can cause tooth decay in their children, according to Stephanie Momeni, a doctoral candidate at the University of Alabama Birmingham.

But a longitudinal genetic analysis of S. mutans strains, conducted in a small Alabama town, suggested that there are many other sources, including other kids, Momeni told reporters at the ASM Microbe meeting.

In particular, she said, about half of the S. mutans strains found in the children over 8 years of follow-up were not shared by their mothers, or by other members of the household, and 72% of the children carried at least one such strain.

The most likely source is other children, she said.

"Children have common sharing behaviors -- 'Here, have a lick of my ice-cream cone' -- that could result in transmission," Momeni said.

The results of the study by Momeni's group are early as only about 13,000 of the 30,000 isolates available for the children and their family members have been evaluated, but they suggest that better understanding of the transmission of S. mutans might lead to better dental care.

"If we can track transmission and if we can identify strains associated with disease, we could develop targeted therapies and better caries risk assessment," she said.

Indeed, if clinicians were aware that children carried an aggressively virulent strain of the bacteria, "they could target them for treatment," even using current tools, commented Michael Schmidt, PhD, of the Medical University of South Carolina in Charleston, and a spokesman for the American Society of Microbiology.

The issue is important because of a cascade of events -- decay in the first dentition predisposes a child to decay in the permanent teeth, and poor oral health in adulthood is a risk factor for heart disease, among other things, he said.

Momeni and colleagues have been studying 119 African-American children and 414 of their household family members in the small town of Uniontown in Alabama's Perry Country, with a population of about 1,800.

They evaluated S. mutans strains using repetitive extragenic palindromic polymerase chain reactions, a method that allows investigators to develop a fingerprint of different genotypes of bacteria or fungi.

All told, Momeni's group identified 34 different genotypes among the samples analyzed so far; on average the children had 2.69 different genotypes, with a range from one to nine.

For each genotype, she said, children were evaluated as either having a match with a household family member or having no match. If there was no match, Momeni and colleagues assumed the strain was acquired outside the home.

Analysis of the children found that 29 children (24%), didn't share any of their genotypes with someone in the household.

Also, 33 (28%) shared all their genotypes within the household.

And 86 children had at least one genotype that wasn't shared with any household family member.

Since the children could have multiple genotypes, the researchers also analyzed the data by genotype, Momeni said.

In that analysis, they found that in 157 cases, among 21 genotypes, the child did not share the genotype with any household member, including 53 cases in which only one one isolate was found, 57 in which two to nine isolates were found over time, and 47 in which 10 or more were found.

The researchers defined the first category as transient infections, the second as borderline, and the third as established infection; about a third of the infections were transient, Momeni noted.

They also found 158 cases among 21 genotypes where a child and a household family member shared the genotype, including 87 where the child shared the genotype with more than one family member.

As expected, they most often shared a genotype with mother (in 54% of cases), but they also commonly shared with siblings (46%) and cousins (23%).

Importantly, Momeni said, about a third of the strains have not been associated with dental caries, while others have been shown to be protective.

The study had support from the National Institute of Dental and Craniofacial Research.

Momeni and co-authors disclosed no relevant relationships with industry.

Schmidt disclosed no relevant relationships with industry.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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